The present invention relates in general to an adaptive receiver for use in a digital communication system using a quadrature amplitude modulation (QAM) technique. More particularly, this invention relates to a method and apparatus whereby a joint operation of an adaptive channel encoding process, an adaptive system filtering process and a process of maximum likelihood sequence estimation (MLSE), by means of a system-characteristics oriented error estimation criterion underlying the present invention, is realized with an unknown data training.
The term QAM is used here in its broadest sense such that said QAM technique includes, in particular, a pulse amplitude modulation (PAM) and a phase-shift keying (PSK) modulation as well as a QAM in its narrow sense that it involves an independent modulation of two quadrature carriers.